Fish Identification Photos: Blue Shark, Prionace glauca: The Blue Shark is the most abundant of the pelagic sharks found on the West Coast. The Blue Shark has an overall blue coloration with a dark blue back, flanks with an intense blue coloration, a white belly, and the anal and pectoral fins are dark.

The Blue Shark has a very elongated body with a head profile that has a long narrow rounded snout. It has five short gill slits, the last two of which are over the pectoral base. The origin of the first dorsal is well behind the exceedingly long, narrow and slightly curved pectoral fins. The caudal fin base has a small keel. The Blue Shark reaches over 16 feet in length and is found at depths up to 300 feet in the water column. The Blue Shark can be confused with two Mako Sharks, the Shortfin Mako, Isurus oxyrinchus (white under snout, head bigger than the pectorals, and first dorsal over the pectoral border), and the Longfin Mako, Isurus paucus (dark under snout, bluntly pointed snout, very small anal and second dorsal fins). Females give birth to as many as 135 eighteen-inch pups per annum. The Blue Shark is found in waters between 52 and 81 degrees, but they prefer 52 to 63-degree temperatures. In Mexico, the Blue Shark is found all along the coast of the Pacific side of the Baja California peninsula and along the coast of the mainland; it is absent from the Sea of Cortez north of La Paz and from around most of the oceanic islands. The Blue Sharks is not a main food species since the meat becomes uneatable very quickly, but the meat is used to produce jerky. The Blue Shark was a food source for Native Americans.

The Blue Shark is a member of the Carcharhinidae Family which includes some of the largest (up to 25 feet in length), most dangerous and best known sharks: the blue sharks, lemon sharks, requiem sharks, sharpnose sharks, tiger sharks, whitenose sharks and whitetip sharks. They are active strong swimmers that travel alone, in small schools, or in large groups. They all have characteristic grooves along their lips, a first dorsal fin that is smaller than the upper lobe of the caudal fin that is situated before the pelvic fins, a much smaller second dorsal fin, and the upper lobe of the caudal fin has an undulating ridge along the top edge. They are voracious predators, feeding on fishes, other sharks, crabs, lobsters, octopi, rays, squid, and shrimp. Globally, 50 species have been identified of which 16 live in Mexican waters. The Leopard Shark is the only global member of the Prionace genus. These sharks are exceedingly dangerous (the family includes the Great White) with a reported 100 attacks on humans per year of which approximately 30 percent are fatal.

Blue Shark, Prionace glauca: Blue Shark chasing mackerel. Photo courtesy Richard Herrmann.